Method for defining the characteristics of metal electrodes of ceramic sensor elements

A method for defining the characteristics of metal electrodes of ceramic sensor elements, where the metal electrodes are deposited as layers and subjected to a subsequent annealing process. The aim is to provide a non-destructive, simple and economical method, capable of being automated, for performing an acceptance test in a specimen-specific manner on the sensor element. In the case of the test procedure proposed here, the quantity and distribution of gold deposited so as to be inaccessible in the protective layer, are indirectly determined. This is done by measuring the layer thickness during manufacturing of an electrode, in a before/after comparison, with the aid of an eddy-current measuring process where the electrode is placed in the magnetic circuit of a coil that is traversed by the flow of a high-frequency a.c. current, and the resulting ostensible inductance of the coil is measured using an LCR measuring unit. The coil can be wired as a resonant circuit with the aid of a capacitor.